The present invention relates to improvements in heat sinks for electronic semiconductor devices, especially so-called plastic power devices having both exposed metallic tabs and plastic-encapsulated semiconductor packages, and, in one particular aspect, to novel and improved resilient one-piece sheet-metal heat-dissipating attachments for miniature plastic power devices which are of low-cost and uncomplicated construction and lend themselves to unique snap-fitting attachments in which they make and sustain intimate broad-area contacts and at the same time exhibit relatively large radiating surfaces and free channels for air circulations.
As electronic semiconductor devices and circuit modules have evolved into ever smaller packaged sizes, problems associated with the dissipation of self-generated heat have intensified, and important power-handling capabilities must be sacrificed unless adequate cooling is realized somehow. Where the environments of use permit it, forced-liquid coolants may be employed, but, quite commonly, thermally-vulnerable regions are safeguarded with the aid of attachments in the form of finned metal extrusions or sheet-metal stampings which will conduct and radiate away heat before it can build up to intolerable levels. In that connection, encapsulated semiconductor devices or packages are sometimes provided with exposed heat-transfer parts, such as relatively thick metal tabs or plates, which promote thermal-energy transfer to such attachments and, in turn, to the ambient environment. Such heat-dissipating attachments may include a resilient spring-clip member cooperating with a heat-dissipating base (as in U.S. Pat. Nos. 3,548,927 and 4,054,901), or such attachments may take the form of a single stamped sheet-metal body shaped both to promote cooling and to hold itself in place (U.S. Pat. Nos. 3,893,161 and 4,012,769 and 4,041,524).
The ease and convenience involved in fitting the heat-sink attachments are important considerations, as are, also, the creation and maintenance of broad-area efficient and effective heat-exchange paths for conductive and convective modes of cooling. When auxiliary tools and fasteners must be used, the fastening operations can become quite awkward, and, if resort must be had to tight springing or clamping to make and hold intimate contacts, it may be difficult to force the heat sink into place and to avoid damage to the device, which may itself be rather small and delicate, and to its frail leads. Accordingly, the present teachings are aimed at reducing such difficulties by way of heat-sink attachments which may be fashioned inexpensively of sheet stock bent to a trough-like configuration from which resilient sides are looped about to form a restricted access opening allowing a miniature semiconductor package to be pressed directly into and yieldably trapped in a mated relationship within the trough.